recently i've noticed that after a post the forum remind me to the homepage instead to the sub-board category (for example if i post in muscolar art section it doesn't remind me to muscolar art board, but to general homepage)
it's a little boring

OK - I don't think this is a site issue because I cannot replicate it. 

I changed the whole authentication system for the site last week, so there will be difficulties until cookies expire and caches are cleared.  My advice is to clear the cache on your browser and the problem may go away.